When should you choose FreeMarker over other template engines like Velocity or Thymeleaf?

The right choice depends mostly on what is being generated and how tightly it needs to look like the final format while being edited.

• Choose FreeMarker when output is not just HTML - e-mails, source code, configuration files, reports - since it was designed around producing arbitrary text, not specifically web pages.
• Choose FreeMarker over Velocity for new projects in general: FreeMarker has a stricter language that catches more template mistakes at parse time, first-class output-format-aware auto-escaping, and materially more active maintenance and releases from the Apache Software Foundation.
• Choose Thymeleaf instead when the priority is "natural templates" - HTML files that remain valid, previewable HTML even before FreeMarker/Thymeleaf processes them, which matters when designers need to open the raw file directly in a browser. This is also why Spring Boot's default starter guidance leans toward Thymeleaf for typical web view rendering today.

None of these differences make one engine objectively "better" in isolation; the deciding factor is usually the output format and who else needs to edit the templates.